The present invention relates to a method and apparatus for coating circuit boards with insulating and/or waterproofing material. More particularly, the present invention relates to the application of a measured amount of an insulating material such as silicone to predetermined locations on a printed circuit board and the hardening of that insulating material into a coating which waterproofs or otherwise insulates the printed circuit board from external influences.
Printed circuit boards are being used in more and more applications in which they are exposed to external influences such as moisture, thermal changes, and vibration. Most importantly, and of dire consequence to the operation of the printed circuit on the circuit board, is the exposure of the printed circuit board to moisture or condensation. For example, the printed circuit boards which are being used in automobiles are often subjected to drastic changes in temperature and humidity such that moisture condenses on the printed circuit board.
To prevent the damage and/or malfunction of the printed circuit board from exposure to elements such as water, the circuit board must be coated with an insulating material. This insulating material is generally silicone or a silicone derivative, but plastic polymers and acrylics can also be coated onto the printed circuit board to provide the necessary protection. Present methods involve the application of the insulating material to the printed circuit boards by either dipping the circuit board into a container of liquid insulating material or spraying the insulating material onto the circuit board. A necessary and time consuming prerequisite to the dipping or spraying of the circuit board is the masking of those components on the printed circuit board which can be damaged by the insulating material itself. For instance, connectors, buzzers, solenoid valves and many other components on the printed circuit board cannot be coated with the insulating material without impairment of their function.
There is, therefore, a need for a method and apparatus which coates the printed circuit board with insulating material without coating those components whose function will be impaired by being coated with insulating material. There is also a need for an apparatus which will coat the printed circuit board with insulating material without the necessity of masking those components which will be damaged by exposure to the insulating material, thereby avoiding the time-consuming and expensive prerequisite of masking those components.
It is, therefore, an object of the present invention to provide an apparatus and method for coating printed circuit boards with insulating material which avoids the necessity of masking sensitive components before application of the insulating material.
Another object of the present invention is to provide an apparatus for coating printed circuit boards with insulating material which comprises a manifold having an inlet in fluid communication with a source of insulating material and a plurality of outlets with a length of flexible tubing attached to each of the outlets, the tubing being selectively bendable to direct insulating material to a predetermined location on a printed circuit board, means for positioning the printed circuit board in preselected, spaced relationship with the manifold, and means for pumping a measured amount of insulating material through the manifold and out the lengths of flexible tubing onto a printed circuit board.
Another object of the present invention is to provide a method of coating printed circuit boards with insulating material comprising mounting a printed circuit board to a conveyor and moving the conveyor, stopping the conveyor when the printed circuit board is under a manifold having a plurality of lengths of flexible tubing mounted thereto, each length of flexible tubing being in fluid communication with a source of insulating material, bending the lengths of flexible tubing to direct a flow of insulating material to a predetermined location on the printed circuit board under the manifold, and delivering a measured flow of insulating material to the printed circuit board through the lengths of flexible tubing.
Another object of the present invention is to provide a method for coating printed circuit boards with insulating material which does not require the masking of the sensitive components on the printed circuit board before the application of the insulating material.
Still another object of the present invention is to provide an apparatus capable of coating both sides of the printed circuit board without immersing the printed circuit board in the insulating material used to coat the circuit board.
Other objects of the present invention will be clear to those skilled in the art who have the benefit of this disclosure from the following detailed description of the invention.